CA2548983C

CA2548983C - Device and method for manufacturing wrapped tubes

Info

Publication number: CA2548983C
Application number: CA2548983A
Authority: CA
Inventors: Karl-Heinz Krah; Adolf Berger
Original assignee: KRAH AG
Current assignee: KRAH AG
Priority date: 2003-11-24
Filing date: 2004-11-09
Publication date: 2011-01-04
Anticipated expiration: 2024-11-09
Also published as: ES2309575T3; US20080193688A1; WO2005053933A1; DK1691967T3; CN1621218A; EP1691967A1; TR200400617A2; SI1691967T1; DE10355073A1; PT1691967E; EP1691967B1; PL1691967T3; DE502004007516D1; ATE399631T1; CA2548983A1; CN100528537C

Abstract

In a device and a method for manufacturing wrapped tubes by helically winding up a thermoplastic, preferably strip-shaped plastic profile (2) onto a winding core (1) in an overlapping manner, where a plasticizing aggregate supplies the plastic profile (2) via a profile nozzle (4), it is provided that the plasticizing aggregate is a kneading means (3) supplying a thermoplastic plastic mixed with reinforcing fibers to the winding core (1) via the profile nozzle (4).

Description

Device And Method For Manufacturing Wrapped Tubes Background of the Invention Field of the Invention The invention relates to a device as well as a method for manufacturing wrapped tubes by helically winding up a thermoplastic, preferably strip-shaped plastic profile onto a winding core in an overlapping manner, a plas-ticizing aggregate supplying the plastic profile via a profile nozzle.

Description of Related Art Devices for manufacturing a tubular object by helically or spirally winding up a band material of thermoplastic plastics are known, for example, from German Patent No. 1281676 issued on October 31, 1968 to Manfred Hawerkamp. Immediately after the band material has emerged from an ex-truder or has been heated, it is wound up, in a deformable state, onto a winding core with an overlapping and/or abutting, particularly obliquely abutting overlapping winding seam and welded by applying pressure and, if necessary, additional heat in the region of the winding seam in such a method.

Summary of the Invention It is an object of the invention to provide a device as well as a method for manufacturing wrapped tubes by which pressure tubes with a larger tube diameter are producible without an extreme enlargement of the wall thick-ness as would bb the case in the present wrapped tube production.

The invention advantageously provides that the plasticizing aggregate is a kneading means supplying the winding core with a thermoplastic plastic mixed with reinforcing fibers via the profile nozzle.

Because of the use of a screw kneading aggregate, reinforcing fibers with greater fiber lengths can also be mixed homogeneously with the thermoplas-tic plastic without shortening or grinding the fibers. The screw kneading ag-gregate permits the exactly metered addition of fibers into the processed molten mass, the fiber length of the added fibers being preserved. The in-crease in pressure-resistance and tensile strength due to the fiber strength-ening permits to manufacture, e.g., larger tube diameters with a tube wall of lesser wall thickness and thus of small weight. Due to the strengthening, pressure tubes with an outer diameter of, e.g., up to 4 m and more are pro-ducible as wrapped tubes.

Such a homogenized mixture of fibers and thermoplastic plastic while pre-serving the fiber length of the fibers cannot be produced by a conventional extruder because of the very high shearing forces, since the fibers are shortened and ground due to the occurring shearing forces.

Preferably, the thermoplastic plastic consists of polyethylene or polypropyl-ene. No granules with fillers are used but polyethylene granules or polypro-pylene granules are plasticized in the kneader and provided with fiber-shaped reinforcing agents, in principle, all strength-increasing reinforcing fibers being suitable.

Preferably, the reinforcing fibers consist of plastic, glass and/or metal, glass fibers in particular, but also aramide fibers and/or carbon fibers being highly strength-increasing.

When several layers of the plastic profile are wound up, this is effected un-der a different supply angle so that the fiber-reinforced superposed winding layers cross each other whereby the internal pressure resistance of the wrapped tubes is additionally increased.

On the outside of the wrapped tube, a profile, preferably a tube profile, may be additionally wound onto the outer tube wall to increase the tube stiffness and the moment of inertia.

The fiber length of the reinforcing fibers amounts to at least about 2 mm, but preferably to more than 4 mm up to endless fibers.

The screw kneading aggregate is adapted to process such fiber lengths up to endless fibers.

The fiber-reinforced thermoplastic mixture homogenized in the screw kneader consists of about 60 to about 94 percent by weight of polyethylene or polypropylene, about 1 to about 10 % of the bonding agent as well as of about 5 to about 40 percent by weight of reinforcing fibers arranged in an uniformly distributed manner in random orientation in the plastic profile.
The bonding agent particularly serves to improve the adhesion between the polyethylene or polypropylene and the fibers.

In addition to the at least one layer formed of the fiber-reinforced plastic profiles, an innermost and/or an outermost winding layer of polyethylene without fiber reinforcement may also be wound up onto the winding core.
According to an aspect of the present invention there is provided a device for manufacturing wrapped tubes by helically winding shaped thermoplastic onto a winding core, the device comprising:
a plasticizing unit for supplying the shaped thermoplastic to the winding core via a nozzle, 3a wherein the plasticizing unit is a kneading means supplying the shaped thermoplastic via the nozzle, and the shaped thermoplastic comprises thermoplastic material mixed with reinforcing fibers, and wherein the kneading means is a screw kneading unit, such that the reinforcing fibers can be homogeneously mixed with the thermoplastic material, while fiber length of the reinforcing fibers is maintained.

According to another aspect of the present invention there is provided a method for manufacturing wrapped tubes by winding shaped thermoplastic onto a winding core in an overlapping manner, the shaped thermoplastic being supplied to the winding core from a plasticizing unit and a nozzle, the method comprising the steps of.
heating a thermoplastic material to a predetermined melting temperature;
homogeneously mixing the heated thermoplastic material with reinforcing fibers in a kneading means, wherein the kneading means comprises a screw kneader and is employed as the plasticizing unit for manufacturing said wrapped tubes with an increased internal pressure resistance; and supplying the fiber-reinforced homogenized thermoplastic material mixture to the winding core via the nozzle.

According to a further aspect of the present invention there is provided a wrapped tube manufactured according to the method as described herein, wherein the fiber-reinforced homogenized thermoplastic material mixture comprises:
- 60 to 94 percent by weight of polyethylene or polypropylene;
- 1 to 10 percent by weight of bonding agent; and - 5 to 40 percent by weight of the reinforcing fibers arranged in random orientation.

3b Brief Description of the Drawings Hereinafter, an embodiment of the invention is explained with reference to the drawings, in which Fig. 1 shows, in side view, a device according to the invention, for manu-facturing wrapped tubes;

Fig. 2 shows the device according to Fig. 1 in top view; and Fig. 3 shows the winding of several winding layers.

Detailed Description of the Preferred Embodiment of the Invention Figure 1 shows a device for manufacturing a wrapped tube by helically wind-ing up a thermoplastic, preferably strip-shaped plastic profile 2 onto a tem-perable or heatable winding core 1 in an overlapping manner.

A screw kneading aggregate 3 used for plasticizing is seated on a reciprocat-ing slide 5 that is adapted to be displaced to and fro along a guide 6 parallel to the winding core 1, the plastic profile 2 being supplied to the winding core 1 from the screw kneading aggregate 3 via a profile nozzle 4.

As can be seen from the top view of Fig. 2, the plastic profile 2 is supplied to the winding core 1 via the profile nozzle 4 under an oblique angle. In the reversal position of the slide 5 at the ends of the winding core 1, there arises an oblique angle with the same amount but with opposite direction because of the reversal of the direction of movement of the slide 5 so that succeed-ing winding layers 9a,9b cross each other. Preferably, it is provided that the start of a new winding layer is respectively effected at different ends of the winding core 1 so that the winding process can substantially be continued continuously. The first plastic profile 2 of a winding layer may also be sup-plied straight to obtain a straight end at the end faces of the wrapped tube.
From Fig. 3, the different orientation of the plastic profile 2 of superposed winding layers 9a,9b is apparent.

While the slide is thus moved to and fro, the winding core 1 rotates to wind up the strip-shaped plastic profile 2 in an overlapping manner, which profile is welded at the points of overlapping and abutment.

The screw kneading aggregate 3 supplies a homogenized mixture of a ther-moplastic plastic of polyethylene or polypropylene and reinforcing fibers of plastic, glass and/or metal to the profile nozzle 4. Upon emerging from the double screw kneader, the fibers are arranged in the mixture so as to be distributed homogeneously in random orientation in the thermoplastic plastic and then, they are supplied to the winding core 1 via the profile nozzle 4.
Preferably, the screw kneading aggregate consists of a double screw kneader where the screws arranged in parallel next to each other do not ro-tate in opposite directions but have the same rotational direction. The kneading means is also referred to as double screw kneader with the same rotational direction. In dependence on the processed mixture, the tempera-ture of the thermoplastic plastic amounts to about 170 to 240 C.

Single-screw as well as double screw extruders rotating in opposite direc-tions, however, are not suited to produce the mixture of fiber-reinforced fi-bers and thermoplastic plastic because they do not have a sufficient ho-mogenizing effect and shorten or grind the fibers because of the occurring shearing forces so that the pressure resistance required for the production of pressure-resistant wrapped tubes with large diameter cannot be achieved.
Preferably, reinforcing fibers of glass fibers are employed, for particular ap-plications and particularly high strength requirements, however, aramide fibers and/or carbon fibers or a mixture of different fibers can be used as well.

The fiber length should amount to at least 2 mm, preferably, however, to more than 4 mm. In a preferred embodiment, the fiber length amounts to about 6 mm. It is also possible, however, to use longer fibers up to endless fibers.

The fiber-reinforced thermoplastic plastic mixture emerging from the screw kneader 3 preferably consists of about 60 to about 94 percent by weight of polyethylene or polypropylene, about 1 to about 10 % of bonding agent as well as of about 5 to about 40 percent by weight of reinforcing fibers.
Therefore, a double screw kneader 3 is used as a plasticizing aggregate for manufacturing wrapped tubes with an increased internal pressure resis-tance, a thermoplastic plastic being brought to a predetermined melting temperature in the double screw kneader 3 and then being homogeneously mixed with reinforcing fibers. Subsequently, the fiber-reinforced homoge-nized thermoplastic plastic mixture can be supplied to the profile nozzle 4.
As a whole, the wrapped tube may be formed of several winding layers, where the innermost and/or the outermost winding layer may be formed of polyethylene without fiber reinforcement. Preferably, the fiber-reinforced winding layers are wound crosswise, i.e., radially adjacent winding layers 9a,9b extend under different angles such that the orientation of the fibers crosses each other in the individual winding layers.

By means of the described device and the manufacturing method, wrapped pressure tubes with large dimensions and very high internal pressure resis-tance are producible, the wall thickness, due to the fiber reinforcement, be-ing substantially, i.e., by about 50%, smaller than with conventional manu-facturing methods without fiber reinforcement.

In a wrapped tube with a diameter of about 4 m, for example, the wall thickness amounts to about 100 mm to 200 mm, each winding layer 9a,9b being formed of a plastic profile 2 with a thickness of about 5 to 10 mm.
Such pressure-resistant wrapped tubes are suitable for the conveyance of drinking water, for example.

As is apparent from Fig. 1, the winding core 1 rotates clockwise so that the plastic profile 2 is wound downward onto the winding core 1, a pressing means 7 pressing the plastic profile 2 against the winding core 1. The screw kneader 3 extends under an angle of 901 to the longitudinal axis of the winding core 1, the oblique angle of each winding layer 9,11 resulting solely from the advance of the slide 5.

Although the invention has been described and illustrated with reference to specific illustrative embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments. Those skilled in the art will rec-ognize that variations and modifications can be made without departing from the true scope of the invention as defined by the claims that follow. It is therefore intended to include within the invention all such variations and modifications as fall within the scope of the appended claims and equivalents thereof.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A device for manufacturing wrapped tubes by helically winding shaped thermoplastic onto a winding core, the device comprising:
a plasticizing unit for supplying the shaped thermoplastic to the winding core via a nozzle, wherein the plasticizing unit is a kneading means supplying the shaped thermoplastic via the nozzle, and the shaped thermoplastic comprises thermoplastic material mixed with reinforcing fibers, and wherein the kneading means is a screw kneading unit, such that the reinforcing fibers can be homogeneously mixed with the thermoplastic material, while fiber length of the reinforcing fibers is maintained.

2. The device according to claim 1, wherein the shaped thermoplastic is strip-shaped.

3. The device according to claim 1 or 2 wherein the thermoplastic material comprises polyethylene or polypropylene.

4. The device according to any one of claims 1 to 3, wherein the reinforcing fibers comprise plastic, glass or metal fibers or a combination thereof.

5. The device according to any one of claims 1 to 3, wherein the reinforcing fibers comprise glass fibers, aramide fibers or carbon fibers or a combination thereof.

6. The device according to any one of claims 1 to 5, wherein the fiber length of the reinforcing fibers is at least 2 mm.

7. The device according to claim 6, wherein the fiber length of the reinforcing fibers is greater than 4 mm.

8. The device according to any one of claims 1 to 7, wherein the wrapped tubes comprise a plurality of superposed winding layers formed of the shaped thermoplastic and extending under an oblique angle relative to each other.

9. The device according to any one of claims 1 to 8, wherein the fiber-reinforced mixture homogenized in the kneading means comprises:
- 60 to 94 percent by weight of polyethylene or polypropylene;
- 1 to 10 percent by weight of bonding agent; and - 5 to 40 percent by weight of the reinforcing fibers.

10. A method for manufacturing wrapped tubes by winding shaped thermoplastic onto a winding core in an overlapping manner, the shaped thermoplastic being supplied to the winding core from a plasticizing unit and a nozzle, the method comprising the steps of:
heating a thermoplastic material to a predetermined melting temperature;
homogeneously mixing the heated thermoplastic material with reinforcing fibers in a kneading means, wherein the kneading means comprises a screw kneader and is employed as the plasticizing unit for manufacturing said wrapped tubes with an increased internal pressure resistance; and supplying the fiber-reinforced homogenized thermoplastic material mixture to the winding core via the nozzle.

11. The method according to claim 10, wherein the shaped thermoplastic is strip-shaped.

12. The method according to claim 10 or 11, wherein the thermoplastic material comprises polyethylene or polypropylene.

13. The method according to any one of claims 9 to 12, wherein the reinforcing fibers comprise plastic, glass or metal fibers or a combination thereof.

14. The method according to any one of claims 10 to 13, wherein the wrapped tube is formed of a plurality of winding layers wrapped on top of each other.

15. The method according to claim 14, wherein the thermoplastic material is supplied to the winding core under a predetermined oblique angle.

16. The method according to claim 15, wherein the plurality of winding layers are wound up continuously, wherein the nozzle is provided on a slide, and wherein when the slide is at a reversal position at ends of the winding core, the oblique angle changes to a different oblique angle with opposite direction due to the reversal of the winding direction in such a manner that succeeding winding layers cross each other.

17. The method according to any one of claims 14 to 16, wherein the innermost and/or the outermost winding layer is wound of polyethylene without any fiber reinforcement.

18. A wrapped tube manufactured according to the method defined in claim 10, wherein the fiber-reinforced homogenized thermoplastic material mixture comprises:
- 60 to 94 percent by weight of polyethylene or polypropylene;
- 1 to 10 percent by weight of bonding agent; and - 5 to 40 percent by weight of the reinforcing fibers arranged in random orientation.